The Yarnell, Arizona blaze that killed 19 firefighters has quadrupled in size since the deaths.

The incidents with the firefighters is the largest single loss of emergency personnel in the U.S. since 9/11. It is the third deadliest loss of personnel in a wildfire in U.S. history.

Arizona Governor Jan Brewer declared a state of emergency for “the deadliest conflagration in state history.” She shard her sympathies with the family members of those lost, saying no one can fully repay the sacrifice of their loved ones.

A spokeswoman for the Southwest Area Incident Command said the fire was “zero percent contained”. Firefighters from all over the southwest are being sent to the region of the fire where 400 firefighters are already working around the clock.

Low humidty and 100 degree temperatures are hampering the efforts of firefights to contain the blaze. Around 250 homes have already been lost to the flames.

Officials now confirm the cause of the fire was a lighting strike.